It is well established that oxygen and circulation are among the key components of any healthy, water-based ecosystem. Plant communities, algae, aerobic, facultative, and anaerobic bacteria provide a benefit to a body of liquid such as a waste water system because they carry on life processes which digest much of the bio-waste polluting these bodies, thus making the facilities more pleasing both in aroma and aesthetics. Many of these living organisms, such as aerobic bacteria, require oxygen to survive, but are immobile. Therefore, aerobic bacteria flourish, as do other organisms with which they interact, when a body of waste water or liquid is circulated. The displacement of these organisms brings them into contact with the nutrients upon which they survive. Because the movement can allow one organism in an ecosystem to interact and influence other organisms, the system is made more complete. Plainly, the interactions of these organisms vary depending upon biological, chemical and physical dynamics of the body of liquid or waste water. This is why engineers in the field have attempted to manipulate these dynamics in order to accomplish a more balanced ecosystem.
It has been established that adding artificial aeration to natural, as well as manmade ponds and lagoons, can greatly increase the health of the ponds. Artificial aeration involves injecting oxygen-containing gas into the depths of a body of water or liquid. The exposure of the liquid to free oxygen allows a system to increase its dissolved oxygen levels and thus, the health of the system. Pumping great quantities of oxygen-containing gas to the depths of a body of liquid requires great energy, and thus monetary expenditures. A plentiful source of oxygen is the atmosphere along the surface of the body of liquid. Because oxygen is naturally transferred to liquid during contact with the atmosphere, the attention of engineers in the field has turned to bringing greater volumes of liquid into contact with that readily available oxygen source.
Many attempts have been made to increase oxygen transfer rates into bodies of water. Accepted conventional methods include: splash-type units which pump large volumes of water discharged in small droplets (10 mm diameter); aspirator units which draw atmospheric air into a propeller and force air bubbles into the water; and, compressor devices which release air from their fixed location at the bottom of the pond. All of these devices are accepted methods of oxygen transfer, and all have inherent disadvantages, including high energy costs, high maintenance costs, inconsistent oxygen transfer rates and turbulent discharges which result in flow interference and small zones of influence.
It has been known for some years that water could obtain a near frictionless or non-turbulent flow at its surface if the correct energy at the correct angle is applied. As the law of inertia would dictate, this flow is interrupted when an outside force acts upon the water molecules. The frictionless flow occurs over the surface of a pond or lake and is commonly known as laminar flow. Laminar flow in this context, is typically interrupted by excess turbulence or waves generated by an aerator device or by the shore embankment where the molecules are turned back. This phenomenon is of particular importance with respect to achieving optimal flow and achieving a much greater zone of influence of the mixing, circulation and distribution of dissolved oxygen throughout the pond. The induction of laminar flow exposes greater volumes of water to the atmosphere. Since the atmosphere is the most readily available source of oxygen in most bodies of liquid, optimal levels of dissolved oxygen transfer may be obtained by the inducement of laminar flow.
The waste water treatment industry is continually expanding to meet the demands of population growth. As infrastructure demands increase, existing facilities must be upgraded and/or new facilities built. Effluent (facility discharge) quality requirements are becoming more restrictive, requiring more efficient technologies for successful operation. The continually increasing cost of power puts new pressure on industry to find more efficient treatment processes and equipment.
Past developments in the art have attempted to circulate waste water but have done so at high energy costs. Other devices, more recently introduced have sought to lower energy costs but have not been successful because they cannot provide oxygen transfer ratings accepted by industry and government. No device to date has successfully circulated liquid in a non-turbulent manner in order to maximize flow and maximize oxygen transfer.
Relatively recent developments in the area have attempted to utilize natural re-aeration processes by pumping water from near the bottom of the lagoon and discharging that water onto the surface. (See Ruzicka et al U.S. Pat. No. 7,121,536 B2.) These systems use less energy than prior treatment systems. As mentioned above, the disadvantage of these systems is a lack of industry-accepted, measured oxygen transfer rates, and their restriction to bodies of liquid with low waste loads. Quantifiable oxygen transfer measurements are required to meet industry standards and governmental mandates. In addition, natural reaeration cannot serve as a primary manner of predictably treating waste water because anomalies in waste can inhibit natural reaeration (e.g. oil slicks caused by petroleum or vegetable oils, and ice in cold winter climates).
More than 80% of the aeration systems utilized in mechanical treatment plants in the USA are diffused air systems, while less than 20% of aerated-lagoon systems use diffused air as their oxygen source. None of the aerated lagoon systems use a low pressure, air-lift pump assisted method of aeration with radially divergent discharge.